Bump-feed filament vegetation trimmer

ABSTRACT

A bump-actuable filament feed for vegetation trimmers; when the cutting length of filament breaks or wears short, the user without interrupting cutting simply bumps the cutting head on the ground deploying a fresh cutting-length of filament. Bumping causes a spring-restored spool latch to yield an increment of spool rotation, feeding a corresponding increment of filament from the spool. For replenishing the filament supply when exhausted, the spool snaps out in one embodiment on pressing a button, and a fresh spool as easily snaps into place. 
     For applications in which bumping the cutting head against the ground is not desired an analogous operation is provided by adaptation of the basic structure.

This is a division of application Ser. No. 713,147 filed Aug. 10, 1976and now abandoned.

This invention relates generally to vegetation cutting and specificallyto a filament trimmer type cutter.

A principal object of the invention is to provide a spool-type supplyfor a filament trimmer overcoming old-art problems of feeding freshfilament from a spool. Customarily in the past it was practice to drawline from such a spool manually with bare hands after manipulation of amanual brake, and after stopping operation of the device.

However, such operation exposes the user to possible injury, and tocontact with vegetation pulp which may contain injurious components suchas poison ivy. In addition, work is interrupted each time a fresh lengthof filament is required, and the user is tempted to continue with aninefficient fragment rather than interrupt trimming for the fraction ofa minute required to up-end the device and draw out a newlength offilament.

In contrast, a new cutting length of filament is deployed in a fractionof a second according to the principal object of this invention duringoperation and without any measuring. This user simply bumps the cuttinghead on the ground or otherwise to deploy a fresh cutting-length offilament, without further thought in the matter.

Further important objects are to provide a mechanism as described whichis flexibly adapted through design-proportion of fixed parts to dispenselarge or small or intermediate length increments, which cannotovershoot, which is actuable through a variety of modes, which isapplicable to a variety of types of cutter heads, eyelet, slot,hollowshaft and the like and which in embodiment provides aself-threading feature in association with the length-modulationfeature.

Still further objects are to provide a mechanism as described whichshields the filament on the spool during operation, and which is safe,economical, durable and simple to operate.

Yet further objects are to provide a method of feeding filament throughor past a rotating guiding means in a filament trimmer which is fast,effective, safe and reliable.

The use of the term "bump" herein denotes that the invention is operableby a sudden impulse in the nature of a jar or shake.

In brief summary, given for purposes of cursive description only and notas limitation, the invention includes a filament feed actuable by a jarto feed a fresh filament cutting length.

The above and other objects and advantages of the invention will becomemore readily apparent on examination of the following description,including the drawings in which like reference numerals designate likeparts:

FIG. 1 is a side elevational view;

FIG. 2 is a sectional elevational view through a first embodiment of theinvention;

FIG. 3 is a plan view in section taken at 3--3, FIG. 1;

FIG. 4 is a developed sectional detail taken at 4--4, FIG. 3;

FIG. 5 is an isometric view of a spool;

FIG. 6 is a bottom plan view of a spool;

FIG. 7 is a sectional elevational detail of an alternative spool mount;

FIG. 8 is a sectional elevational view of a second embodiment of theinvention;

FIG. 9 is a sectional elevational detail of a third embodiment of theinvention;

FIG. 10 is a sectional elevational detail of a fourth embodiment;

FIG. 11 is a sectional elevational detail of an alternative cup designfor the invention; and

FIG. 12 is a detail viewed at 12--12, FIG. 11.

FIG. 1 shows a typical filament trimmer T of the hand held type, withthe present invention 10 installed as a cutting head beneath it inposition for filament-increment feed by bumping the ground (arrow) withthe cutterhead.

FIG. 2 shows the invention in compact embodiment 10 as in the previousFigure connected for rotation by the driveshaft 16 of a filament trimmerso that the filament free end 18 extending from wound filament supply18a will swing as a cutting length in a circle about the axis of thedriveshaft.

THE HOUSING

Housing 20 has an inverted-cup shape with interior protrusions. The hub22 of the housing is fitted to the driveshaft with a key or spline 24,and a cylindrical wall 26 extends down from the perimeter of the hub.

A circumferentially spaced set of fixed stops 28 protrudes radiallyinwardly from the wall of the housing and a set of circumferentiallyspaced fixed lugs 30 protrudes down from the hub in staggered relationto the stops and axially offset from them. The filament cutting length18 protrudes outward through faired guiding aperture 32 in the housing.

THE SPOOL

The spool 34 is slidably held on the driveshaft at the bore 36 by a nut37 against the downward bias of compression spring 38 bearing on thehousing at one end and held in annular opening 40 in the spool at theother end.

Filament is wound about the spool between the lower flange 42 and theupper flange 44.

The lower flange has at the bottom an upward taper 46 and a centralcounterbore 48 for fastening to the end of the drive shaft, as by thewingnut and a washer 52.

The upper flange of the spool has at least one and preferably a pair ofdiametrically opposed spool-latching tabs 54 on a radius and at an axialposition causing the tabs to rest squarely against respective fixedstops 28 in the housing.

OPERATION OF FIRST EMBODIMENT

Operation is as follows: the entire unit is rotated as a cutting headunit by the driveshaft (arrow) in cutting grass or the like with thecutting length 18 of filament. The filament supply is oppositely woundto the direction of operational rotation. During operation, when thefilament becomes frayed or broken, the operator merely bumps the bottomof the unit on the ground to feed a precise increment of filamentthrough the faired aperture 32.

Bumping slides the spool 34 upward to a position shown at 34' in phantomlines, freeing the integral spool-latching tabs from the stops 28. Thisinstantaneously permits the centrifugal force of the cutting length offilament, and the slight slowing of rate of rotation of the spool byground contact, to rotate the spool relative to the housing through anarc interrupted when the tabs 54 strike lugs 30. The restoring force ofspring 38 then snaps the spool down to the initial level, on which thetabs rotate to a position of rest against the stops as before, but inthe incrementally advanced rotational position noted. The spring forceis in the direction aiding the unit to bounce back clear of the groundwhen bumped, and to lessen stresses of bumping.

FIG. 3 shows in diagrammatical plan the circumferentially staggeredrelation of the housing fixed stops 28 and lugs 30 respectively locatedbetween the stops, with tabs 54 of the spool resting against two of thestops.

Obviously the invention offers great flexibility of feed, since theincrements of feed can be large or small, depending on the number ofstops and lugs provided. It is believed that most operators will be ableto bump-out two increments of feed in two seconds if it is desired toprovide half-length increments, for example. Obviously, at least onestop and at least one lug or equivalent and at least one tab arerequired for wear-and stress-reduction.

FIG. 4, a detail adapted from 4--4, FIG. 3 diagrammatically details inside elevation the path of a tab (arrows) from one position to the nextin interaction of the tabs 54, stops 28 and lugs 30.

Each lug is less wide than the space between stops minus twice thetab-width to permit the tab to rise when bumped and to fall when lodgedagainst the lug in mid-cycle of the feed.

FIG. 5 shows a spool 34 in isometric view. The spool is proferably ofmaterial that can be molded or cast such as plastic, with unitaryspool-latching tabs 54, lower and upper flanges 42, 44 respectively,tapered bottom 46 to facilitate proper bumping, and annular springgroove 40 in the upper face of the upper flange. The spring groove maybe tight enough to retain the spring, making one fewer separate part ifa resupply of filament is to be wound on the spool by the user.

The filament is in any case secured at the inner end to the spool, anyconventional means may be used for this, symbolized by hole 56 throughthe lower flange, through which the filament end may be run and thenknotted below.

FIG. 6 shows the bottom plan view of the spool 34 as having ribs 58,which may be used, if desired to increase friction on bumping in heavyor wet grass or the like.

PUNCH-RELEASE SPOOL RETAINER

FIG. 7 illustrates in alternative embodiment 700 a punch-releasemechanism 760 for snap-in/snap-out spool attachment.

The spool 734 and housing are similar to that previously described, butthe spool bore 736 has an annular enlargement 762 in upwardly spacedlocation from the lower end of the spool.

The driveshaft 716 has opposed captive balls 764 in a transverse bore766. A spring 768 forces a captive plunger 770 down in a coaxial hole inthe shaft, forcing the balls radially outward, engaging the upper end ofthe annulus and retaining the spool against the urging of spring 738compressed between the spool and hub 722.

OPERATION OF SPOOL RETAINER

To release the spool, the operator reaches upward into the bore andpresses the protruding end of the plunger upward against the bias of thespring 768 until the reduced-section portion 770a of the plunger is atthe level of the balls. The balls then retract into the reduced-sectionportion of the plunger under the urging of spring 738 as it acts throughthe spool on the incline of the balls, and snaps the spool free.

To install a spool is simply a matter of pushing it onto the shaft withplunger depressed after which upon release of the plunger the ballsengage the annular recess in the spool and retain the spool.

In manufacture, the balls and the plunger may be retained by staking orother conventional means.

HOUSING UPWARD-ACTUATION EMBODIMENT

FIG. 8 illustrates a further embodiment 800 in which the spool 834 isfixed to the driveshaft 816 as by key 824 and punch-release mechanism860, and the housing 820 is slidable upward on the shaft against thebias of shoulder spring 838 when bumped upward. The resultant relativemotion between the spool means and housing means releases thespool-latching tabs 854, which may be constructed with upward offset asshown, to fly around under drive of the shaft, lodge against lugs 830,and advanced, relocate against stops 828 as before under restoring biasof spring 838. The exchanged locations of the lugs and stops will beevident in this embodiment.

OPTIONAL METHOD OF PUMPING

Bumping may be by means of a tap of the lower edge of the housingagainst the ground, be done inertially by means of a shake or it may bedone through a ground-contactor handle or a fist-tapped handle which byconventional means raises circular flange 872 on top of the housing bymeans of a fork 873. The fork may also limit downward travel of thehousing in the manner of a stop, whether or not used to lift. Fist orpalm or foot bumping of a conventional lever system to raise the forkmay be preferred to actuate the escapement in lawnmower installations asopposed to hand carried filament trimmer installations.

This Figure also indicates that the principle of this invention isequally applicable to slot configurations 32a in the housing, and toeyelet configurations.

HOUSING DOWNWARD-ACTUATION EMBODIMENT

FIG. 9 illustrates an embodiment 900 for a trimmer with a hollowdriveshaft 916 in which the housing 920 is fixed in rotation to thedriveshaft as by key 924. The filament 918 runs down the bore 974 of thedriveshaft through an aperture 976 below the spool, and the housing isslidably held on the drive shaft against the upward bias of a spring 938between spool and housing. A nut 978 on the upper end of the shaftretains the housing. The filament leads down and emerges as a cuttinglength at any conventional cutter head, such as a drum (not shown) withan eyelet.

OPERATION OF HOUSING DOWNWARD-ACTUATION EMBODIMENT

To actuate the filament feed of this embodiment, the housing may bebumped downward by a fork or finger 972 under any suitable pumpingactuation, or may be actuated by a bump of the cutting head to releasethe spool and permit it to be drawn through the feeding arc.

HOLLOW-SHAFT SPOOL-LIFT ACTUATION EMBODIMENT

FIG. 10 illustrates an embodiment 1000 similar to that of thefirst-described embodiment illustrated in FIG. 2, except that thehousing 1020 is fixed as by nut 1078, shoulder 1080 and key 1024 at thetop of a hollow shaft filament trimmer with the filament 1018 runningaround the top downward through the hollow shaft 1016. The spool may bebumped upward for actuation by a fork 1072 which may be bumped up byground contact or otherwise, by conventional type frame-attached orother linkage. A hollow shaft filament feed of different type isdisclosed in U.S. Pat. No. 3,928,911 issued Dec. 30, 1975, to Charles B.Pittinger, Jr. for HOLLOW-SHAFT FEED FILAMENT TRIMMER.

FIGS. 11 and 12 are respectively side elevational sectional detail andside elevational detail of any housing of the types described above buthaving an outwardly preferably elliptical convex bulge 1182 around thefilament aperture, which aperture may be a circumferential slot 1132.Centrifugal force will tend to funnel a filament free end 1118 which maybe snapped-off inside the housing into the slot upon bumping-feed of afilament increment, making this in effect an automatic-threadinghousing. Obviously if the wall is thick, a local interior concavity willserve the same function.

It will be appreciated that the driveshaft itself can be modified toserve the function of one of the elements, upper or lower, hereindescribed, within the spirit of the invention.

It will be appreciated also that the invention can safely shield thefilament wound on the spool, and that in the hollow-shaft embodiment, itoffers two modes of down-the-shaft feed, both isolating the entiremechanism from the cutting head while supplying useful flywheel momentumenabling minimal structure to be employed at the cutting head, and thatthe various other types of operation are applicable also to thisembodiment.

This invention is not to be construed as limited to the particular formsdisclosed herein, since these are to be regarded as illustrative ratherthan restrictive. It is, therefore, to be understood that the inventionmay be practiced within the scope of the claims otherwise than asspecifically described.

What is claimed and desired to be secured by U.S. Letters Patent is: 1.In a filament trimmer mechanism for cutting materials includingground-growing vegetation by swinging a filament free-end as a cuttinglength, means for storing filament for resupplying said cutting length,and means for deploying in succession lengths from the storing means forsaid resupplying, the improvement comprising: the means for deployingincluding means responsive to impulse actuation for feedingpredetermined lengths of filament, means for securing filament followingsaid feeding, the means responsive including first means, second means,one of said first and second means including said means for storing, theother of said first and second means including means for guiding, meansfor positioning the first means and the second means movably relative toeach other for responding to said impulse actuation, the means forpositioning including a driveshaft, the first means including means forguiding a said cutting length of filament, the first means havingslidable coupling for rotation with the driveshaft, the second meansincluding said means for storing, the first means movable along thedriveshaft from a first position to a second position, the means fordeploying comprising means permitting rotation of the second means atsaid first position, the means for securing comprising means preventingrotation of the second means at said second position, means for biasingthe first means toward the second position, the driveshaft being hollowand having an upper end and a lower end, the first means and the secondmeans being toward the upper end of the driveshaft, and means providingfor a said filament to extend from the second means and the guidingmeans through at least a portion of the driveshaft for deploymenttherefrom as a cutting length.
 2. In a mechanism as recited in claim 1,the means providing including an aperture in the hollow shaft below thefirst and second means for passage of a said filament therethrough. 3.In a filament trimmer mechanism for cutting materials includingground-growing vegetation by swinging a filament free-end as a cuttinglength, means for storing filament for resupplying said cutting length,and means for deploying in succession lengths from the storing means forsaid resupplying, the improvement comprising: the means for deployingincluding means responsive to impulse actuation for feedingpredetermined lengths of said filament, means for securing filamentfollowing said feeding, the means responsive including first means,second means, one of said first and second means including said meansfor storing, the other of said first and second means including meansfor guiding, means for positioning the first means and the second meansmovably relative to each other for responding to said impulse actuation,the means for positioning including a driveshaft, the first meansguiding a said cutting length of filament, the second means includingsaid means for storing, the first means having coupling for rotationwith the driveshaft, the second means movable along the driveshaft froma first position to a second position, the means for deployingpermitting rotation of the second means at said first position, themeans for securing preventing rotation of the second means at saidsecond position, means biasing the second means toward the secondposition, the driveshaft being hollow and having an upper end and alower end, the first means and the second means being toward the upperend of the driveshaft, and means providing for a said filament to extendfrom the first means and the guiding means through at least a portion ofthe driveshaft for deployment therefrom as a cutting length.
 4. In amechanism as recited in claim 3, the means providing including a saidend of the hollow shaft being open for passage of said a filament.
 5. Ina vegetation-cutting filament trimmer of the type having a rotatablehollow driveshaft mounting a spool concentric in a housing and filamenton the spool passing from the spool through an opening in the housinginto and down said hollow driveshaft for deployment from a lower portionof said hollow driveshaft as a predetermined cutting length undercentrifugal force on rotation of the hollow driveshaft, the improvementcomprising: the hollow driveshaft having structure defining an aperturelaterally therein below said spool, and said filament passing throughthe aperture prior to passing as said, into and down said hollowdriveshaft.
 6. In a vegetation cutting filament trimmer of the typehaving a spool concentric in a housing, a length of rotatable hollowshaft mounting concentrically at an upper portion thereof the spool andhousing, filament on the spool and passing through the housing anddeployable from the hollow shaft as a cutting length of filament at aposition below the spool under centrifugal force of said rotating, theimprovement comprising: the hollow shaft having structure defining anaperture therein intermediate the length thereof, and the filamentpassing in predetermined lengths from said housing through said apertureinto the hollow shaft and down to said position below the spool.
 7. In arotary filament trimmer for trimming vegetation and being of the typehaving: a spool, a housing around the spool concentric with the spooland a hollow shaft attached to and extending below the spool andhousing, the improvement comprising: the hollow shaft being attached atan upper end thereof to the housing and rotatably attached to the spool,filament on the spool and having an end passing through an opening inthe housing and down the hollow shaft for deployment as a predeterminedlength of vegetation trimming filament under centrifugal force onrotation of said hollow shaft, and the housing and spool together havingmeans for releasing additional predetermined lengths of said filamentfor passage down the hollow shaft under centrifugal force on rotation ofthe hollow shaft and housing relative to said spool.